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United States Patent |
5,137,830
|
Milly
|
August 11, 1992
|
Post-compression method of measuring soil gas concentration and emission
Abstract
Measuring of soil gas flux. Particularly a method of measuring soil gas
concentration and emission flux during a period of post-compression of the
earth's crust. The method includes observing gravitational acceleration on
the surface of the earth, as defined by crustal tension and compression
and as induced by the Sun and Moon, compensating for variation in
acceleration due to geographic location of said observing, locating said
crustal tension in the form of a bulge on the surface of the earth, then
post-compression measuring of soil gas concentration and emission flux
rate during both the long term (approximately 1 to 10 days) and short term
(approximately 1 to 8 hours) of maximum soil gas emission.
Inventors:
|
Milly; George H. (Middletown, MD)
|
Assignee:
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Quadrel Research Corporation (Middletown, MD)
|
Appl. No.:
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308283 |
Filed:
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February 9, 1989 |
Current U.S. Class: |
436/25; 367/60; 436/32; 436/81; 436/122; 436/139 |
Intern'l Class: |
G01N 033/24 |
Field of Search: |
436/32,29,25,139,81,122
367/60
|
References Cited
Other References
Klusman, Ronald W., Jaacks, Jeffrey A.; "Environmental influences upon
Mercury, radon, and helium concentrations in soil gases at a site near
Denver, Colo." J. Geochem Explor 27(3) 259-280 See CAS abstract #59851e.
|
Primary Examiner: Housel; James C.
Assistant Examiner: Daley; Thomas E.
Attorney, Agent or Firm: Semmes; David H.
Claims
I claim:
1. Post-compression method of measuring soil gas concentration and emission
flux, so as to minimize effects of natural variability and to enhance
measuring sensitivity comprising:
a) observing gravitational acceleration on the surface of the earth in the
form of earth tides as defined by crustal tension and compression and as
induced by the sun and moon;
b) compensating for variation in acceleration due to geographic location of
said observing;
c) locating said crustal tension in the form of a bulge on the surface of
the earth, said bulge extending in the direction of the vector sum of the
forces of the sun and moon; and
d) post-compression measuring of soil gas concentration and emission flux
rate during periods of maximum soil gas emission.
2. Post-compression method of measuring soil gas concentration and emission
flux as in claim 1, including:
e) restricting said post-compression measuring on a long term basis to
approximately 1 to 10 days for measuring average post-compression soil gas
concentration and emission flux rate, during periods of maximum average
semi-diurnal gravitational acceleration occurring within the lunar month;
and
f) further restricting said post-compression measuring on a short term
basis to approximately 1 to 8 hours for measuring soil gas concentration
and emission flux rate during the post-compression phase of a single
semi-diurnal gravitational acceleration maximum occurring within the lunar
month.
3. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, said measuring of soil gas flux including adjacent
measuring of atmospheric concentration of said soil gas.
4. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, wherein said soil gas is in the form of gaseous radon.
5. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, wherein said soil gas is helium.
6. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, wherein said soil gas is hydrocarbon from oil and gas
deposits.
7. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, wherein said soil gas is mercury vapor.
8. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, wherein said soil gas consists of volatile inorganic
compounds of boron, arsenic and antimony.
9. Post-compression method of measuring soil gas concentration and emission
flux as in claim 2, wherein said soil gas consists of volatile organic
compounds emitted from buried toxic wastes.
10. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas consists of
semi-volatile organic compounds emitted from buried toxic wastes.
11. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas is acid fumes.
12. Post compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas is sulfur compounds.
13. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas is carbon dioxide.
14. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas is water vapor.
15. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas is of natural origin.
16. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, wherein said soil gas is of anthropogenic
origin.
17. Post-compression method of measuring soil gas concentration and
emission flux as in claim 2, including compensating for variation in
acceleration due to geographic setting.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
Method of measuring soil gas emanation. Particularly a method of measuring
both soil gas concentration and emission flux as an aid to oil and gas
exploration, minerals exploration, evaluation of polluted sources and the
like.
2. Description of the Prior Art
Introduction
The present method of measuring said gas concentrations and emissions
enables the control of planning and scheduling of soil gas and atmospheric
sampling as a means of geological and geophysical exploration and
evaluation, and of detecting and assessing buried natural and
anthropogenic substances by reference to natural geophysical phenomena.
More specifically, this invention enables an enhanced measuring of soil
gas concentrations and emission flux rates, with favorable and unfavorable
periods being delineated upon the calculation of the curve of variation of
earth tidal forces, and the empirically determined relationship of soil
gas concentration and emission flux rate to the tidal forces. The novelty
and utility of the invention in a variety of applications is discussed
below. For many years various kinds of measurements have been made based
on soil gases occurring near or at the surface of the earth and in the
atmosphere as a means of detecting and otherwise characterizing source
materials buried below the surface and from which such gases arise.
Several examples may be cited.
Oil and Gas Exploration
In the oil and gas industry, geological exploration has included detection
of hydrocarbons arising from accumulations at depth. In the early days of
oil exploration, visible seepage of liquid oil out of the earth enabled
detection of deposits near the surface. Later, more sensitive seep
detection techniques were employed based on the upward migration of gases
arising from volatile components of deeper deposits. Direct Techniques of
"micro-seep" detection are based on the hydrocarbons arising from the
source deposit itself; indirect techniques are based on non-hydrocarbon
gases that may be associated with the deposit, e.g. a radon halo or
anomalous concentrations of helium.
Direct techniques have received the most attention and include:
a) microbiological methods based on certain microorganisms that thrive on
hydrocarbons that have migrated to the surface (G. G. Soli,
"Microorganisms and Geochemical methods of Oil Prospecting", Bulletin of
Amer. Assn. of Petroleum Geologists, v. 41, no. 1, pp. 134-40, January
1957; Stravinski, "Microbiological Method of Prospecting for Oil", World
Oil, v. 141, no. 6, pp. 104, 106, 109-110, November 1955); and
b) the development of certain carbonates formed upon hydrocarbon exposure
that can be detected by controlled thermal cycling and monitoring the
evolved carbon dioxide from near-surface soil samples (E. McDermott, U.S.
Pat. No. 2,590,113, Geochemical Prospecting).
Methods (a) and (b) involve long term exposures to hydrocarbon gases
thereby providing stable averaging. However, these techniques are subject
to specific near surface characteristics and to important logistic
disadvantages: complex analytical techniques, and resultant delays in
obtaining results, important to the conduct of grass roots exploration;
and possible non-specificity of the method with respect to hydrocarbon
sources. Further, these methods do not identify individual hydrocarbons or
their relative proportions.
The most frequently employed and accepted gas tracer methods involve direct
measurement of the hydrocarbons in soil gas in order to avoid the
difficulties cited above. The gas sample is generally obtained by drawing
air from a sealed off short drill hole into a collecting medium, or by
aspirating soil gas through a metal probe driven several feet into the
ground. The collected samples are then analyzed for specific hydrocarbons
associable with a source deposit, e.g. a series of low molecular weight
alkanes or alkenes and various aromatic compounds. Parallel applications
involve sampling the atmosphere (G. H. Milly, U.S. Pat. No. 3,734,489) or
the ocean bottom (G. J. Demaison and I. R. Kaplan, U.S. Pat. No.
4,659,675) into which the hydrocarbons have emanated. It is relevant to
the present invention as discussed further below that these more generally
employed direct soil gas techniques provide nearly instantaneous snapshots
in time of the hydrocarbon concentration although, as we shall show, the
concentration typically fluctuates widely over short periods of time; and
conventional soil gas surveys pursuant to the usual grid or fence sampling
plan are accomplished with temporally sequential measurements. The
resultant asynoptic data cannot be validly compared point to point in
mapping the soil gas hydrocarbon field because of the varying
concentrations over the time span of measurements. The present invention
provides a time span sampling protocol that accommodates the natural
phenomena responsible for large fluctuations of concentration, and thereby
remedies the deficiencies of prior techniques.
Minerals Exploration
In the metals mining industry, tracer gas techniques have been most notably
employed in exploration for uranium and for gold. In the case of uranium,
the related pathfinder gas is the noble gas radon (Rn-222) arising in the
radioactive decay chain of uranium. Although gold itself has no gas phase,
it frequently occurs in association with mercury compounds and small
amounts of free elemental mercury resulting from biochemical or
geochemical reduction of mercury salts. Even though mercury has a low
vapor pressure (approximately 0.001 mm Hg), this is sufficient to produce
detectable soil gas concentrations.
The variability of soil gas concentration has been widely experienced in
uranium exploration--where the techniques have been extensively
employed--to the extent that irreproducibility of measurments has led to
an attitude of distrust of the technology as other than a supporting but
often suspect adjunct to more familiar methods.
Other potential applications of presently employed gas tracer techniques in
a variety of other mineral exploration applications here involve
considerations similar to those discussed above. These include: mapping
phosphate beds based on radon emission from low level uranium content
therein; exploration for sulfur deposits in salt domes, based on emission
of gaseous sulfur compounds, carbon dioxide, and radon; exploration for
geothermal sources; exploration for subsurface water bodies in desert
regions based on water vapor emission. All present similar complications
with respect to previously unexplained variability in relation to
presently employed gas tracer techniques. Even carefully controlled
experiments of radon gas concentration over a 13-month period (R. L.
Fleischer and A. Mogro-Campero, Geophysical Research Letters, pp. 362-4,
May 1979) have led to admitted lack of explanation of the variation and
speculations as to in-earth convective cells that our data indicate not to
be a correct interpretation.
Evaluation of Pollutant Sources
In the area of toxic materials management, soil gas techniques are
applicable in the detection and evaluation of buried substances, either
naturally occuring or anthropogenic in nature and not readily detected by
other surface techniques.
(i) A prominent example of a naturally occurring hazard is radon emitting
into residences, schools and other buildings. Evaluation of large
statewide areas to define high and low risk regions can be done using
atmospheric sampling techniques to map regional variations in radon
emission intensity (G. H. Milly, Mobile Measurement of Radon Concentration
in East Coast Terrain, U.S. Environmental Protection Agency Contract No.
68-01-7341, February 1987, Quadrel Research Corporation). As in the case
of uranium exploration based on soil gas radon, large variations in
emission rate can and do typically occur over a period of several hours.
Depending on when the measurements are made, an area actually presenting a
substantial threat can appear harmless. Another example of natural
pollutants relates to sulfur compounds, and practical concerns of their
role in acid rain. Emission rates have been measured employing a large
area sampling grid over the eastern United States to assess the fractional
contribution of natural sulfur to industrial sulfur dioxide and sulphate
loadings of the atmosphere. (D. F. Adams et al., Biogenic Sulfur Emissions
in the SURE Region Electric Power Research Institute, EA-1516, Project
856-1, September 1980). However, potentially large temporal variations
across the non-simultaneous but serial grid-point measurements were not
recognized or accommodated.
(ii) Anthropogenic hazards are represented most pervasively by numerous
widespread toxic chemical waste sites where toxic industrial and
commercial materials have been dumped and then covered over with earth.
Waste site investigations involve various methods of detection and
evaluation of the content and area perimeters of subsurface contamination
including measurements of volatilized vapors of buried contaminants
contained in soil gas. Post-closure monitoring after clean-up may also
employ soil gas techniques. Current practice of soil gas mapping entails
sequential point to point sampling over an area array. The problems
previously cited regarding temporal variation are such that, under certain
conditions, misleadingly little or no emission is detectable; and, under
favorable conditions for emission, short term variability distorts the
true pattern because of asynoptic observations. Similar considerations
apply to other anthropogenic hazards such as radon emissions from uranium
mill tailing piles.
Summary
In summary, there are numerous examples of economic and public health
importance where assessments may be made on the basis of measurements of
soil gas either directly, or indirectly through resultant atmospheric
concentration; and the utility or even validity of these techniques is
readily thwarted by wide variations in emission rates and resultant
atmospheric concentration levels. Applicant explains this variation and
provides a method for enhanced measuring of soil gas, so as to control
planning and scheduling of measurement programs and minimize or eliminate
the effect of variability; while providing enhanced comprehension in the
analysis of data by recognizing the source of these variations.
SUMMARY OF THE INVENTION
Post-compression method of measuring soil gas concentrations and emissions
so as to minimize effects of natural variability and to enhance
measurement sensitivity. The method is characterized by defining
gravitational acceleration on the surface of the earth induced by the sun
and moon, calculating the vertical component of the gravitational
acceleration vector and compensating for variation and acceleration due to
geographic location; then post-compression measuring of soil gas
concentration during periods of maximum soil gas emission. The
post-compression method of measuring may be restricted both to the long
term (approximately 1-10 days) and the short term (approximately 1-8
hours) for maximum average semi-diurnal gravitational acceleration.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view depicting earth's crustal tension/compression
sequence.
FIG. 2 is a graph depicting the vertical component of gravitational
acceleration over a selected 3-month period.
FIG. 3 is a graph depicting the vertical component of gravitational
acceleration over a selected 1-month period.
FIG. 4 is a graph depicting the vertical component of gravitational
acceleration over a selected 5-day period.
FIG. 5 is a graph depicting the typical tidal acceleration curve depicting
the earth crustal compression sequence.
FIG. 6 is a graph depicting three-day time series of emission flux rate and
gravitational acceleration intensity.
FIG. 7 is a prior art graph depicting comparison of radon concentration in
soil gas with average range of gravitational acceleration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The fluctuation in soil gas concentration and emission flux rates over
relatively short periods of time is a recognized phenomenon that has been
previously studied. Much of the work is based on radon as a naturally
occurring test gas because it is an ubiquitous and convenient substance
for this purpose. These studies have suggested that meteorological factors
are responsible for some portion of the variation. Most frequently noted
are wind speed, soil temperature and rainfall, and barometric pressure
changes (Kramer et al., "Measurements of the Effects of Atmospheric
Variables on Radon-222 Flux and Soil Gas Concentrations", The Natural
Radiation Environment, Adams and Lowder, eds., 1964; Klusman, R. W. and
Webster, J. D., "Meteorological Noise in Crustal Gas Emission Relevant to
Geochemical Exploration", J. Geochem. Explor., v. 15, pp. 63-76, 1981;
Clements, W. E. and M. H. Wilkening, "Atmospheric Pressure Effects on
.sup.222 Rn Transport Across the Earth-Air Interface", J. Geophys. Res.,
v. 79, no. 33, pp. 5025-29, Nov. 20, 1974). Of these, pressure change may
be the most important by inducing a kind of pumping action, drawing soil
gas upward and out of the earth during falling pressure and reducing or
suppressing emission during increasing pressure. Applicant's experiments
have shown however, that meteorological factors fail to explain the
frequency, time of occurrence, and magnitude of the observed fluctuations.
Rather, applicant's experiments have shown that by far the dominant causal
mechanism is the phenomenon known as earth tides.
Earth tides, analogous to ocean tides and atmospheric tides, consist of
ellipsoidal deformation of the earth's otherwise normal oblate spheroid
shape. The deformation is brought about in response to the gravitational
acceleration induced by the earth's principal celestial neighbors--the
moon and the sun. As the earth rotates on its axis, and as it progresses
on its orbit around the sun (the ecliptic), meanwhile being itself orbited
by the moon, the earth is subjected to gravitational pull resulting in a
bulge in the direction of the vector sum of the forces of these two
external bodies, and a reflectant antipodal bulge. As the earth rotates
while progressing in its orbit, the gravitational acceleration is
experienced as sweeping over the earth with a vector magnitude and
direction dependent on latitude, longitude and elevation above sea level
of the point of observation on the earth. The cyclic variation in
gravitational acceleration felt at any specified point is aperiodic in
that it is not a precise repetition of a wave-like function but displays
variations dependent on the ever changing positional and attitudinal
relations among the three bodies.
The practical result of these interactions is that the region of the earth
experiencing maximum acceleration will be subject to crustal tension due
to distortional stretching as will its antipodal region, while the
intervening areas will experience a compensating collapsing crustal
compression (FIG. 1). As the earth rotates, a given geographic point will,
therefore, be subjected to alternating tension and compression. Under
conditions of tension, the earth's crustal porosity increases, and
fractures, fissures and microcracks expand, thereby opening up routes of
escape of soil gases from within the earth toward the surface and across
the earth-air interface into the atmosphere, while at the same time
permitting these routes to be filled with interiorly generated gases as
well as inspired volumes of the ambient atmosphere. During the following
period of crustal compression, these openings become closed to their
minimum levels, thereby expelling the aforementioned soil gases that have
entered the open voids. The process of closure is capable of inducing very
high gas velocities in the earth contrary to the generally held assumption
that vertical gas migration is by molecular diffusion. Our experiments
indicate that transport velocities within the earth often are several
orders of magnitude (up to 10,000 times) greater than diffusion
velocities.
We have found the phenomenon of earth tides, as illustrated below, to be
the dominant factor in producing repeated and frequent large fluctuations
of soil gas emission flux rate and; that these fluctuations are
secondarily modified by meteorological variables. The geologic setting of
a particular location is a constant, and so can affect the absolute
magnitude and range of variation in soil gas concentrations and emission
flux rates, but the fundamental pattern of variation persists.
An understanding of the variation in gravitational acceleration enables
improved design of observational programs and interpretation of resultant
data. For maximum sensitivity of detecting buried sources of soil gas
constituents, it is advantageous to make measurements during periods of
maximum emission flux rate and to avoid periods when emission is at a
minimum or suppressed entirely. It is, therefore, essential to know the
time of occurrence and duration of periods of maximum emission in order to
plan more precisely the timing of short term observations or the
scheduling of more extended time-averaged measurements. The present
invention enables such determinations and thereby enhances control of
planning and scheduling of soil gas measurements so as to optimize their
validity and effectiveness. In order to practice this invention, one must
(1) define by calculation and prediction gravitational acceleration as a
function of time for a given location and (2) specify periods of both
maximum emission and minimum emission within the curve of variation of
gravitational acceleration. Because of the complexity and tediousness of
the calculations, the calculation of tidal force can be done most
conveniently by computer methods. These calculations can be done by means
of previously published methods (Longman, I. M., "Formulas for Computing
the Tidal Accelerations Due to the Moon and the Sun", J. Geophys. Res., v.
64, no. 12, pp. 2351-2355, December 1959; H. N. Pollack, "Longman Tidal
Formulas: Resolution of Horizontal Components", J. Geophys. Res., v. 78,
no. 14, pp. 2598-2600, May 10, 1973). Innovation in this invention
consists in the manner in which computations of gravitational force are
employed as one component of a system of control and analysis of
measurement programs related to soil gas concentration and emission flux
rates. The second question having to do with specification of favorable
measurement periods within the tidal acceleration cycle, i.e., the
relationship between variations in gravitational force and variations in
emission rates, is discussed in the following section.
Experimental Results
Experimental data are presented below to illustrate the effects of tidal
forces as described above and further to confirm reduction to practice of
this invention. The data consist of several categories:
(1) examples of calculated gravitational acceleration curves depicted on
several time scales as used in planning and control of observational
programs,
(2) examples of variation in atmospheric concentrations related to phase of
the tidal phenomenon,
(3) examples of measured emission flux rates related to phase of the tidal
phenomenon,
(4) examples of practical application of radon surveys to the detection of
anomalies relatable to uranium mineral deposits,
(5) examples of the detection of atmospheric mercury anomalies, and
(6) examples of detection of buried toxic wastes.
Examples of calculated gravitational acceleration curves are shown in FIGS.
2, 3 and 4.
FIG. 2 illustrates the overall form of variation when viewed over an
arbitrarily chosen period of three months. Only the vertical component of
the lunar-solar gravitational acceleration is shown, i.e., the component
perpendicular to the earth's surface at the location for which
calculations are made. Applicant has found the vertical component to be
the determining factor in affecting soil gas emission flux rate. It will
be noted that the outer envelope of the cyclic function shown corresponds
closely to the lunar or anomalistic month of 27.55 days and is well known
as the M.sub.1 period of the tidal function. Favorable times for soil gas
measurement are those corresponding to the envelope maximum as is
demonstrated below.
FIG. 3 shows the variation in the vertical component of gravitational
acceleration on a more expanded scale corresponding to a period of one
month. It will be seen that the acceleration intensity varies within the
lunar month with maximum near full and new moon resulting in spring tides,
and minimum at first and last quarters (in the dark) of the moon resulting
in neap tides. The average time of 14.76 days between spring tides
illustrates the fortnightly interval from full moon (in opposition) to new
moon (in conjunction) and is distinguished from the lunar fortnightly
interval of 13.66 days which is the time for the moon to change
declination from zero to maximum and back to zero.
Further expansion of the time scale in FIG. 4 shows the vertical component
of gravitational acceleration over a range of five days centered on a
lunar monthly maximum. This period is chosen for further examination
because it corresponds to the most favorable period within an acceptably
favorable period of about ten days for soil gas and related atmospheric
observations. In this display, it will be seen that there is a
semi-diurnal variation corresponding to the M.sub.2 lunar tidal mode, with
a period of 12 hrs. 25 mins. due to rotation of the earth and a diurnal
period of 24 hrs. 50 mins. due to rotation of the earth and declination of
sun and moon.
For short term soil gas observations, it is shown below that the
semi-diurnal maxima within the lunar month maxima at full and new moon are
important determinants for effective measurement of soil gas emissions.
For longer term averaging measurements over a period of several days, the
monthly maxima correspond to periods of maximum emission flux rates.
The relationship between variation in gravitational acceleration as
described above and the corresponding soil gas behavior can be illustrated
by several kinds of data. Atmospheric concentrations of gases emitted from
the soil are proportional to the rate at which the gases are emitted,
although the actual concentrations are additionally influenced by
meteorological and terrain conditions. Consequently, when emission is low,
air concentrations are low and vice versa. This feature has been
repeatedly observed. By making a series of measurements under comparable
meteorological conditions over the same piece of terrain at various times
in the tidal cycle, the effect of earth tides on emission flux rate can be
demonstrated. In a more direct way, emission flux rate can be measured
continuously over time through various phases of the tidal cycle, thus
permitting delineation of a relationship between tidal acceleration and
emission rate that is less dependent on meteorological considerations.
Operational applications of both kinds have been made, examples of which
are given below, based on naturally occurring radon (Rn-222) as an
ubiquitous and convenient chemically inert test soil gas arising in the
radioactive decay chain from uranium.
As a result of the discoveries made relating emission to tidal cycle,
extensive exploration projects have been conducted using radon as a tracer
gas to discover uranium ore bodies. Using this method of tidal planning
and control some 200,000 radon observations have been made in the Western
United States over an area of some 70,000 square miles, and in Canada and
France. Ore bodies have been discovered by this method and over 34 million
pounds of uranium reserves proven by development drilling on the initial
discovery.
Operational examples follow involving both atmospheric concentration
measurements and the direct measurement of emission flux rates.
EXAMPLE NO. 1
Atmospheric Concentrations Downwind of a Soil Gas Emission Source
Measurements were made of the daughter products of radon in the low level
atmosphere by vacuum collection on micropore filters, followed by counting
alpha radiation with an alpha scintillation/photomultiplier detection and
counting system. The measurements were made under nighttime conditions of
near-surface temperature inversion and low wind speed in an area of west
central New Mexico. Profiles of alpha activity were measured on nine
different nights along a 15 mile route subject to katabatic airflow and
under similar meteorological conditions. The peak activity measured along
the profile was projected back to the source 10 miles upwind to obtain a
relative measure of emission intensity. The slight variation in wind speed
among experiments (range 1.8-3.9 mph) was taken into account in
calculating the time at which the emission occurred that resulted in the
measured peak. Nearly all the measurements were made during the period of
one of the two monthly tidal force maxima, but with different projected
emission times in relation to the semi-diurnal cycle.
The relative emission intensities were averaged according to phases in the
earth tidal compression period with the following results:
______________________________________
Average Relative
Earth Tidal Phase
Emission Intensity
______________________________________
Compression 487
Post-Compression
2,159
Pre-Compression
788
______________________________________
The results are shown against the tidal curve in FIG. 5 where it may be
observed that the maximum emission flux rate occurs in the
post-compression phase of the tidal force cycle at a time interval of 7 to
14 hrs. after the principal tidal force peak. Emissions prior to and after
the post-compression phase are substantially reduced.
EXAMPLE NO. 2
Atmospheric Concentrations in the Vicinity of a Soil Gas Emission Source
A further series of experiments was conducted to illustrate the effects of
short term variation in the gravitational force. Atmospheric radon
daughter ions were measured in the immediate vicinity of the same source
as in Example No. 1 above, over a span of hours involving the semi-diurnal
variation. A total of 13 experiments were done, each on a different night
and under comparable low wind and inversion conditions. On each
experiment, 30 to 50 samples were taken. The time at which the maximum
concentration in each experiment was measured was determined as a lag past
the preceding semi-diurnal peak. The relative emission intensities
represented by the peak concentrations were averaged according to time
intervals with the following results:
______________________________________
Time Past Dirunal
Average Relative
Tidal Peak, Hours
Emission Intensity
______________________________________
0-7 293
7-14 1,517
14-23 454
______________________________________
The pattern of variation is similar to that of Example No. 1, the values
here being consistently in the range of 60% to 70% of those in the
preceding example, the difference in magnitude being due to differences in
location of measurement and consequent differences in age of the
atmospheric radon cloud and development of daughter ions. Hence, the
pattern of FIG. 5 is applicable to this example, and nearly identical with
a 65% scale factor on emission intensity.
EXAMPLE NO. 3
A Three-Day Time Series of Emission Flux Rate Over a Naturally Occurring
Radon Source
In contrast to the two preceding examples based on atmospheric
concentrations, direct evidence of the dependence of emission flux rate on
gravitational acceleration and the resultant earth tidal response was
obtained by making serial observations of emission flux at a fixed point.
These results may then be compared with the calculated curve of
gravitational force. Measurements of radon emission flux rate were made in
a uraniferous area of central Wyoming; consecutive 15 minute samples were
taken over a period of three days at a time of a fortnightly peak in tidal
acceleration. The comparison curves of flux and acceleration are shown in
FIG. 6. The peaks in emission rate following each semidiurnal maximum
tidal force are seen to occur in the post-compression phase encountered in
the two preceding examples, and fall within the same period of
approximately 7 to 14 hours following the tidal peak. The spiked form of
the emission rate is a result of stick-slip phenomena within the earth as
rock adjusts in a succession of slips to the tidal stresses. The
relatively high intervening "background" emission rates are due to
elevated concentrations of uranium in the surface layer of the earth.
The technique of measurement involved a closed container placed on the
earth's surface so that external wind effects were eliminated. Suggestions
in the literature that higher temperatures result in gas expansion and
increased emission rates were found to be without effect inasmuch as the
maximum emissions were observed in the pre-midnight hours when surface
temperatures were lowering. The principal meteorological variable of
concern is barometric pressure. However, the regularity of the diurnal
emission maximum is not consistent with typical variations in barometric
pressure of a significant magnitude, nor with the observed pressure record
which showed little variation. These results support the cycle of
gravitational acceleration and the resultant earth tidal force as a
controlling factor in the application of soil gas measurement techniques.
This example shows that even short term soil gas emission rate is strongly
dependent on time within the luni-solar cycle. For long term sample
collection periods of several days, it is sufficient to choose a time when
peak force within the semi-lunar month is high. The resultant averaging
process will include the intervening short period low values but
nevertheless give rise to maximum integrated flux rates. For short time
measurements, i.e., instantaneous to averaging over several hours
duration, it is important to make observations within the post-compression
period of about 7 to 14 hours following the individual maximum.
EXAMPLE NO. 4
A Thirteen-Month Time Series of Soil Gas Concentration Over a Naturally
Occurring Radon Source
As mentioned above under Description of the Prior Art--Minerals
Exploration, a thirteen month series of soil gas concentration of radon
conducted by Fleischer and Mogro-Campero showed time variations that they
were unable to explain. Their results are shown in FIG. 7 alongside
applicant's calculation of the intensity of gravitational acceleration.
Even though only monthly values are plotted, the parallelism between the
curves is supportive of applicant's findings concerning the dominant role
of tidal forces. This is especially noteworthy inasmuch as all other
environmental or meteorological variables are neglected in the comparison.
EXAMPLE NO. 5
Evaluation of a Buried Toxic Chemical Waste Site
A toxic waste site in Massachusetts was studied by measuring at several
points the emission of hydrocarbon vapors of the various buried chemical
substances. Control of the measurement program was done in accordance with
the methods of this invention. Specifically, an eight day period of
collection of emissions was centered on a fortnightly tidal maximum.
Analysis of the samples revealed the presence of eight contaminants:
1,1-dichloroethylene; ethyl benzene; 1,1,1-trichloroethane; benzene,
toluene; chloroform; tetrachloroethylene; and 1,2-dichloropropane. Of
these compounds, two (1,1-dichloroethylene and ethyl benzene) had been
previously identified by the site owner through drilling and sub-surface
soil sampling. Subsequent to the emission measurements further drilling
was undertaken by the owner and three more of the eight emissions
confirmed (1,1,1-trichloroethane; benzene; chloroform) and an additional
one (toluene) suspected, but not positively identified. The problem of
pre-determining depth from which to draw samples when the depth of the
various toxics is unknown renders exhaustive recovery uncertain. In
contrast, contaminants occurring at all lower levels, are sensed by the
emission techniques employed in conjunction with tidal scheduling.
APPLICATIONS
Summarizing the foregoing discussion and experimental results, the
invention described here consists of a method of measuring soil gas
concentrations, soil gas emission flux rates, and atmospheric
concentrations of soil gases, so as to minimize the effects of natural
variability in these quantities; and obtaining a higher degree of
observational sensitivity by measuring during maximal periods of emission
and concentration; and thereby obtaining a high degree of reproducible
results. Accomplishment of this method of control is based on calculation
of the time function of gravitational acceleration felt at a point on the
earth in response to the sun and the moon; including the conduct of long
time averaged measurements during fortnightly periods of high
acceleration; and the conduct of short time measurements during the
post-compression phase of the semi-diurnal cycle within a semi-monthly
maximum period.
Since the method of control constituting this invention applies to the
movement and emission of any gases from within the earth, it is relevant
to an array of applications based on measurements of soil gas
concentrations, emissions and resultant atmospheric concentrations.
Without limiting the application of this invention, examples are given
below in which soil gas techniques are enhanced by practice of this
invention:
a) Mineral exploration for uranium based on atmospheric concentrations
and/or emission flux rates of gaseous radon and/or helium.
b) Mineral exploration for mercury, gold and other precious and base metals
geochemically associated with mercury or mercury compounds, based on
atmospheric concentrations and/or emission flux rates of mercury vapor
and/or associated volatile compounds such as, for example, those of
arsenic and antimony.
c) Mineral exploration for oil and gas based on atmospheric concentrations
and/or emission flux rates of a spectrum of hydrocarbon compounds, and/or
of radon and helium haloes.
d) Exploration for sub-surface sulfur deposits, especially in salt domes,
based on atmospheric concentrations and/or emission flux rates of hydrogen
sulfide, sulfur dioxide and carbon dioxide that arise in the process of
sulfur deposition; and radon arising from uranium precipitated by chemical
reduction from the overlying ground water due to passage of the
aforementioned sulfur compounds.
e) Exploration for sources of sub-surface water bodies in desert and arid
regions based on atmospheric concentrations and/or emission flux rates of
water vapor.
f) Exploration for geothermal sources based on anomalously high emissions
of associated volatile compounds such as, for example, boranes.
g) Exploration for phosphate minerals and mapping of buried phosphate beds
based on typically high geochemical association of uranium and resultant
radon emissions.
h) Exploration for and mapping of gaseous methane as a fuel source
occurring in association with coal beds.
i) Exploration for and mapping of sub-surface coal deposits based on
emission of methane.
j) Any and all other mineral exploration applications where a gas phase
substance is or can be associated with the mineral target.
k) Area mapping of the regional distribution of radon emission intensity in
relation to environmental concerns about radon concentrations in homes,
schools, and other buildings, as a means of identifying threat areas for
more detailed follow-up inside structures.
l) Evaluation of radon emmision levels on land parcels under consideration
for sale, purchase, or construction thereon, with regard to potential
environmental threat inside buildings.
m) Evaluation of buried toxic chemical waste sites to include
identification of pollutants by recovery of vapor emissions without
surface intrusion; mapping of extent, periphery and areal distribution of
relative intensity of the identified pollutants based on emission of
pollutant vapors; and the detection, tracing and mapping of leachate
plumes of contaminants based on emissions of pollutants and/or radon,
where radon emissions permit mapping of preferred leachate routes such as
rock fractures.
n) Long term post-closure monitoring of toxic chemical waste sites
following waste site remediation procedures in order to monitor variations
in subsurface pollutant beyond the confines of the remediation site.
o) Evaluation and monitoring of uranium mill tailings piles for radon
emissions as a polluting constituent of the atmosphere, based on emission
flux rates and atmospheric concentrations.
p) A means of providing improved, more accurate and representative
determinations of source strengths of both natural and anthropogenic
buried substances in the evaluation of local air pollution exposure,
potential and effects.
q) A means of providing improved, more accurate and representative
determinations of source strengths of sulphur compounds of natural origin
as opposed to industrial sources, in connection with the evaluation of
acid rain effects and policy.
r) A method of experimental control in the prediction of earthquakes based
on fluctuations of radon concentration in response to stress buildup, by
providing a base curve of tidally induced radon concentrations against
which anomalous deviations can be better judged in relation to earthquake
potential.
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